Like all products in the market if your seeking are bargain you might get a bargain and you might get stung.
The reason why people can get stung is anything will work perfect for a short period of time. Anything at all. So people assume well it did work so it must be right and the same dodgy product is sold again.
Buying the cheapest product often means it will have no warranty and designed to fail. It also will not be compatible with future changes resulting in more cost. The cheaper product is only cheap based on a short time frame, over a longer period the cost can be many times more than a good product.
Some designed to fall apart in 2-3 years need replacing at that rate and assure constant replacement and constant cost.
Removing old and unused antennas is important for many reasons like giving your new antenna a clear view for the highest signal level, keep your roof safe and in some cases protecting your neighbors roof yet we still see these all over the place. Possibly for a cheaper price or a dodgy installer? In any case is it worth it?